Sciencemadness Discussion Board - Nitration of Cinnamaldehyde ....help?

Nitration of Cinnamaldehyde ....help?

drahcir_dier - 3-8-2012 at 22:15

Howdy folks!

Recently I've been trying to nitrate some cinnamaldehyde (from cinnamon oil), and have been experiencing some difficulties. I was therefore wondering whether anybody here might be able to shed some light on the matter.

The method I've been trying is as follows:

60ml of concentrated H2SO4 was chilled in an ice bath. 10g of potassium nitrate was added slowly, with stirring. The mix was allowed to cool, and 5g of cinnamon oil added drop wise, while stirring. Once all of the oil is added, the mix is covered, allowed to warm slowly to room temperature, and left over night.

These initial steps do not present any difficulty. My problem comes about when I try and do the work up, to obtain my nitrated product. The theory was that simply diluting the acid mix into ice water should dissolve all the inorganic compounds, leaving the low solubility, nitro-cinnamaldehyde products to precipitate. Sadly this seems to be a particularly naive view.

Adding the acid mix to water generates exceedingly large amounts of foam, presumably as dissolved NO2 is liberated. This foam can be dispersed to leave a dark red-black solution, with what can only be described as a 'dark oily gunk'... This substance seems have the right solubility properties for nitro-cinnamaldehyde, (insoluble in water, soluble in both acetone and ethanol).. but that doesn't really mean anything. No amount of dissolving, concentrating and cooling produces anything other than the same gunk.

I tried extracting the water solution with DCM (Distilled from paint stripper) today, but evaporating off the isolated DCM layer only gave the same black mess.

I am using Momar brand 'MO-FLO drain cleaner' for the acid. This product has its own brown colouring, and so Im not sure how much that is contributing to the colour of the solutions and gunk at the end. Has anybody used this product successfully in nitration reactions? Or have any idea of its concentration or purity? I believe the product MSDS said something like >90%...

Also, I wasn't sure whether some other constituents of cinnamon oil were messing up the reaction, and so also tried purifying the cinnamaldehyde via the bisulfite adduct prior to nitration. Unfortunately, using the isolated cinnamaldehyde didn't seem to make any difference.

So: can anybody see anything glaringly wrong in my procedure? has anybody attempted/succeeded with a reaction like this? And can anyone offer any advice as to what I might do to improve results? Also, it is to be noted that although I would love to try distilling the cinnamaldehyde to ensure high purity, and using the acetic anhydride/acetic acid nitration method to obtain the pure ortho isomer, these processes are well outside my range of capabilities right now.

Cheers.

P.S. I can try and take some pics if that will help.....

Nicodem - 4-8-2012 at 10:29

Quote: Originally posted by drahcir_dier

So: can anybody see anything glaringly wrong in my procedure? has anybody attempted/succeeded with a reaction like this? And can anyone offer any advice as to what I might do to improve results? Also, it is to be noted that although I would love to try distilling the cinnamaldehyde to ensure high purity, and using the acetic anhydride/acetic acid nitration method to obtain the pure ortho isomer, these processes are well outside my range of capabilities right now.

Please provide the pertaining references. You can't expect everyone who read your post knows what you were doing. How do you know that what you obtained is a substance? Which "nitrocinnamaldehyde" you are talking about - what is supposed to be the desired product of such a reaction?

Quote:

P.S. I can try and take some pics if that will help.....

It would help, if you can post pictures of TLC's of the crude.

drahcir_dier - 4-8-2012 at 19:05

The desired product here is the ortho isomer, with the eventual aim of synthesising Indigo. OrgSyn has a procedure for nitration of cinnamaldehyde:

http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4...

They use the acetic anhydride/acetic acid/nitric acid method to obtain pure o-nitrocinnamaldehyde. I've not found any described methods for the sulfuric acid/potassium nitrate method, only passing references:

"The direct nitration of cinnamaldehyde with potassium nitrate in sulfuric acid yields o-nitrocinnamaldehyde"

Also, I don't know that the substance is one compound. Im certain it's not. That is why I am asking if anyone else has attempted this before.

With regards to the TLC, I've only just started experimenting at home, and so I dont yet have access to any form of chromatography....

Nicodem - 4-8-2012 at 23:57

Quote: Originally posted by drahcir_dier

It seems to me that this nitration is based on a pretty extreme case of a chaperon effect. In this case you can forget about achieving the same effect in sulfuric acid.

Quote:

I've not found any described methods for the sulfuric acid/potassium nitrate method, only passing references:

"The direct nitration of cinnamaldehyde with potassium nitrate in sulfuric acid yields o-nitrocinnamaldehyde"

I suggest you to read that ancient Berichte article where this nitration in sulfuric acid is described. You can't just make up experiments based on secondary sources. You should always check the original source whenever possible, also because the full sentence is: "The direct nitration of cinnamaldehyde with potassium nitrate in sulfuric acid yields o-nitrocinnamaldehyde along with p-nitrocinnamaldehyde." Thus, by reading the article you will find out what the para/ortho ratio is.

Quote:

With regards to the TLC, I've only just started experimenting at home, and so I dont yet have access to any form of chromatography....

Unfortunately, there is not much preparative chemistry that can be done in organic synthesis unless you have TLC plates as a minimum. I suggest you to either buy them or make them yourself (there is a thread dedicated on do-it-yourself TLC plates on this forum).

kristofvagyok - 5-8-2012 at 02:05

Quote: Originally posted by drahcir_dier

The desired product here is the ortho isomer, with the eventual aim of synthesising Indigo. OrgSyn has a procedure for nitration of cinnamaldehyde:

http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4...

They use the acetic anhydride/acetic acid/nitric acid method to obtain pure o-nitrocinnamaldehyde. I've not found any described methods for the sulfuric acid/potassium nitrate method, only passing references:

"The direct nitration of cinnamaldehyde with potassium nitrate in sulfuric acid yields o-nitrocinnamaldehyde"

ccH2SO4 and KNO3 instead of acetyl nitrate? You are a funny chemist

I think that it would be better to make an acetal from the aldehyde, so the CHO group would be stable and it wouldn't get oxidized from the fuming nitric/sulfuric acid.

Also some analytical method would be good. Even to identify has any product formed instead of tar, and if yes, that it is just one isomer or is it a mixture of them.

Waffles SS - 27-8-2013 at 06:20

Does Nitration of Cinnamic acid by Acetic anhydride/acetic acid/nitric acid lead to pure ortho isomer like Cinnamaldehyde or not?

ScienceSquirrel - 28-8-2013 at 13:38

You may have some product there but it is sitting in a load of goo.
A little goo goes a long way.
I have seen a black tar yield 60% pure product after chromatography.
Chromatography is near to essential in organic chemistry.